tail light flashing

[Grim]

I've been doing a bit of work of the car lately, in an attempt to fix some obvious mot fails. One is the rear tail lights flashing with the indicators. Due to a myriad of crappy corroded crimp connectors, corroded wiring etc, I've replaced the light wiring back about 6 feet, replaced the light housings (I had replacements in stock, purchased in 2010!) but still the issue persists.

I've fed in a secondary earth from the lights to the chassis and from chassis to battery with no change. Putting a voltmeter on the tail light feed shows the voltage fluctuates as the indicator flashes so there's obviously some resistance upstream of the lights but within a common feed from the battery. I've removed the fuses and wire brushed them (pretty grotty) and that has reduced the voltage fluctuation from 1.5v down to 1v. My plan for tonight is to do the same for the indicator stalks, lighting relays and battery isolator. 

Is there anything else I should look for?

Andy

Edited December 14, 2020 by Grim

[IanS]

rear lights flashing with the indicators normally due to bad earth.

I would check by running a single (no joints) wire all the way from the light cluster back to the battery, can be done quickly round the outside as you are checking.

Fluctuating voltage could be because you are not measuring to a good earth.

Electrical oddball faults (other than blown fuse) I always start by checking the earths resistance back to the battery, I have a long negative lead for my meter to do this.

[Grim]

I found a voltage drop on the column switch feed wire from the fusebox, which I've temporarily replaced and it pretty much solved the problem.